The phrase “dynamic range” refers to the variance between the brightest and darkest points in a photograph. The human eye has the ability to see details within a very broad dynamic range – in fact, the dynamic range that the human eye can discern details within is at least twice as broad as the best digital camera on the market today. And today’s digital cameras can detect a broader range than film cameras. Additionally, the digital camera’s dynamic range capabilities exceed the range capabilities of digital and off-set printing, as well as film processing.
To tap into the details in areas of extreme highlight and shadow, we must compress the dynamic range to bring the brightest brights and the darkest shadows into a range that our computer monitors and printers can handle. So, oddly enough, in order to create an “expanded dynamic range” photo, we end up compressing the dynamic range – not expanding it. Yet, in the end, a larger range of light and shadow becomes visible.
There is another technique called HDR (High Dynamic Range) where the photographer takes 3 or more separate exposures – one “correct”, one over exposed (to bring out shadow detail) and one under exposed (to bring out highlight detail). If you want more information on HDR – just google it, there are tons of sites dedicated to HDR.
But what if you only have a single exposure? My expanded dynamic range technique allows you to (quickly and easily) squeeze expanded dynamic range from a single photograph – restoring detail to the shadow and highlight areas with a minimum of time and effort required.
When shooting in the RAW file format (as opposed to JPEG), your files are saved in either 10-bit, 12-bit or 14-bit format. This means that there is much more color data per pixel than can be displayed on your monitor – or can be transfered to a printed page or photograph – so, clearly, you will get the best results if you are shooting RAW, but this will still work with a JPEG file. Whether your original photo was shot RAW or as a JPEG, make sure that you are working in 16-bit color space (”Image >> Mode >> 16 Bit/Channel”) in Photoshop.
Duplicate your background layer twice. I call the middle layer “Multiply” and the top layer “Screen”. Set the Screen layer’s blending mode to “Screen” and set the opacity to “60%”. The 60% number is usually a good starting point, however, I will sometimes go as high as 100% and as low as 30% – it all depends on the photograph, and this is a real seat-of-the-pants kind of decision. Once you’re familiar with the technique, you’ll be able to figure out the proper value very easily.
Set the Multiply layer’s blending mode to “Multiply” and set the opacity to “60%” as well. The photo will look like crap right now – don’t worry – it’s supposed to, and it’ll look a lot worse before we’re done.
Now, Right-click on the screen layer (in the “Layers” palette) and choose “Blending Options” from the contextual menu. Towards the bottom, you will see a section titled “Blend if: ” – leave the menu set to “Gray”. There are two sets of sliders – we are interested in the top one. Option-click (Alt-Click on a PC) on the white slider marker – this will cause the marker to split in two – drag the left half of the marker all the way to the left, and hit “OK”.
Now we need to do a similar step on the Multiply layer. Only this time, we’re going to split the black marker and move it all the way to the right. The resulting image still probably looks like crap. The mid-tones usually get very muddy right about now – that’s OK.
At this stage, I typically combine all of the layers into one – you can use SHIFT-OPTION-COMMAND-E (SHIFT-ALT-CONTROL-E on a PC) to copy the visible layers into one merged layer, which I normally name “Merged”. I will normally run Auto-Contrast & Auto-Levels on this merged layer. However, if either of those steps causes the image to look worse, undo it and continue on.
Now that we have compressed the dynamic range of the image’s tones, we need to make some adjustments to the tonal range so the image has a more natural appearance. We do this by using the “Image >> Adjustments >> Shadow/Highlight…” tool. Make sure the “Show More Options” box is checked – otherwise, the tool is pretty much useless.
Each photo will require a different set of adjustments, but the values shown above for “Shadows” & “Highlights” are usually a good starting point. One little trick I have discovered is that in almost all cases, you’ll want the 3 sliders to form a diagonal line. As you are moving the sliders around, be sure to toggle the “Preview” button frequently so you can see if your changes are having a positive or negative impact.
Sometimes, this tool can cause some banding in highly saturated color regions. If so, use the “Color Correction” slider. You may even want to use this just to boost the overall saturation even if no banding is visible.
The last step is to adjust the “Midtone Contrast”. Slide it to the left to increase shadow/highlight contrast – to the right to increase the contrast in the mid range.
That’s all there is to it. Let’s take a look at the “Before” & “After” photos…
Notice how much more detail we can see in both the shadow regions as well as in those bright clouds. Even the midtones are much more vibrant.
There are certainly other ways to achieve a similar effect – I have just found this to be the simplest/fastest method. Once you get familiar with where all of these commands live in Photoshop and get a good feel for how the Shadow/Highlights tool behaves, you’ll be able to apply this type of adjustment in under 60 seconds.
Enjoy!
(updated 9/3/09 (:43 am)
P.S.
I just read a related post on Scott Kelby’s blog. Although I have not seen how he is doing it, I suspect that the technique described above is somewhat similar to Scott Kelby’s “Expanded Definition Processing”.